I'm actually in the same situation with you as well. I just upgraded my Rega Carbon (default cartridge from RP1) to Nagoka MP-110 and the improvement is good. I have upgraded the belt from the black one to the white belt. So far the best improvement came from changing the cartridge, which makes perfect sense. Changing the belt only improves the accuracy of the RPM rather than the sound quality IMO.

I'm using Musical Fidelity V-LPS II phono preamp which is connected to my integrated amplifier Krell S-300i. Is there a sound quality change you heard when upgrading the platter mat and the plastic platter?

Just on the Rega fono mini, my dealer said he felt it could only be improved by spending over £300, and I've been v happy with mine. It does benefit from careful siting, but no complaints on the sound. Maybe yours is substandard for some reason?

I'm actually in the same situation with you as well. I just upgraded my Rega Carbon (default cartridge from RP1) to Nagoka MP-110 and the improvement is good. I have upgraded the belt from the black one to the white belt. So far the best improvement came from changing the cartridge, which makes perfect sense. Changing the belt only improves the accuracy of the RPM rather than the sound quality IMO.

I'm using Musical Fidelity V-LPS II phono preamp which is connected to my integrated amplifier Krell S-300i. Is there a sound quality change you heard when upgrading the platter mat and the plastic platter?

Yes that particular platter and the matching double thickness mat has made a world of difference. I am totally using that place for any other little tweaks I fancy trying too. I didn't realise how resonant and noisy the original acryllic and wool setup was.....the new mat is kinda sticky on one side when you wash it and scrub too which they say is awesome for holding the record in place and they do a spray treatment that sucks the static off the record, and it works because after you put a record down on it then turn it over the back of your hand doesnt fuzz up anymore.

Also yeah my ebay listing of the Rega Fono Mini will be honest. Someone always buys the item though even if you say it wasn't for me. It'll be like £40 anyway.